"Duke's 20th Century Frames" were advertised in Cycling Weekly in
1948/49. They said that Duke's had been "Cycle Builders Since 1910".
They also advertised the "Duke Atomic Age of Cycle Constuction" stating
that there frames were hand-built and no jigs were used.
Their
premised were at 6 Boot Street, London N1. Most advertisments and
references to the firm were 1948/9.

Detail shots of the Duke with
its USWB construction

Thisframe
seems puzzling in that it has rear-opening (track) ends with a gear
hanger. The reason for this is that with forward-facing ends the
wheel would have to move forward to be removed from the frame.
The detail shot of the rear half shows just how close to the
bottom bracket area the wheel is although positioned well back in
the ends. Were the ends to be forward opening it would be just
about impossible to remove the wheel even with the tyre deflated - Peter Underwood